Packing for gas cooled electric machines



July 10, 1934. A. SCHNETZLER PACKING FOR GAS COOLED ELECTRIC MACHINES Filed Feb. 17, 1933 INVENTOR @001; Sam/721 ORNEY Patented July 10, 1934 UNITED STATES PACKING FOR GAS COOLED ELECTRIC MACHINES Adolf Schnetzler, Zurich, Switzerland, assignor to Mascliinenfabrik Oerlikon, Oerlikon, Switzerland, a corporation of Switzerland Application February 1'7, 1933, Serial No. 657,199 In Switzerland February 13, 1932 2 Claims.

This invention relates to bearings for gas cooled electric machines. In. order to prevent the escape of gas or the entrance of air in such machines, stuffing boxes are provided that insure absolute tightness with as little friction as possible at the places where the shafts pass through the frame. For this purpose, stuffing boxes have been heretofore used in which a liquid, usually oil, is utilized as a packing medium. These boxes, however, are disadvantageous, in that a strong vortical motion is imparted to the liquid, due to the circumferential velocity of the shaft, which action causes the liquid to escape from the bearing in an atomized state and to thereby carry off with it a relatively large amount of gas in the form of small bubbles, rendering the economy of gas cooling, as compared with air cooling, altogether problematical. While in some cases means are resorted to for recovering the gas thus carried off and lost, the arrangements needed for such purpose are very complicated, and also tend to decrease operating safety to a considerable degree.

In carrying out the invention, a stufiing box is provided in which a current of steam is used as a packing medium, which current is directed against the gas and incoming air respectively and counterbalances both, the steam thus entering the gas and exterior air respectively. The steam, after passing through the stuffing box, is then liquefied in a condenser connected with the box. The foregoing produce the following advantages: A current of steam preventing the escape of gas is constantly maintained in the stufiing box. Then, after the steam has passed through the stufiing box and has mixed with the gas, they are both cleanly separated from each other by means of condensation, except for a minute residue. Moreover, undue loss of gas through withdrawal of the steam is prevented because the latter leaves the condensing chamber in a liquid state, no stufiing box being needed for the same, but merely a packing against the withdrawing liquid. The stufling box itself may be constructed in a form similar to those used in steam turbines.

The accompanying drawing shows a transversesectional elevation of the bearing constituting the invention.

The steam under pressure flowing from a suitable source, not shown, passes through a tube 1 connected to an annular chamber 3 of the stuffing box 2 which carries the shaft 4 of the electric machine, and the steam then passes along said shaft partly to the right, as viewed in the drawing, where it escapes into the air, thereby preventing the entrance of air, and partly to the left, where it leaves the stufiing box and enters into a suitable condenser 5 located within the gas filled machine 511 adjacent to the stuffing box and surrounding the shaft 4. The condenser 5, having therein a tubular coil 5b through which cooling water flows causes the steam to become condensed and liquefied, and in this form it is automatically withdrawn by gravity and by means of a siphonshaped tube 6 connecting the interior of the condenser with the exterior atmosphere. Since the steam pressure in chamber 3 is always maintained a little higher than the gas pressure in the interior of the generating machine 5a and condenser, there will always be produced a current of steam from said chamber to the condenser 5, which will completely prevent the escape and loss of gas.

The condensation product is suitably distilled to extract the gas, and the liquid reconveyed to the boiler. The gas recovered in distilling the condensation product is likewise reconveyed to the generating machine. In a similar manner, the steam escaping from the stufling box directly into the air, at the right thereof as viewed in the drawing, is condensed, and the liquid and gas reconveyed to the boiler and machine respectively, to effect maximum economy. The steam for the stufling box is preferably produced in a special boiler, the feed water of which is softened previously and also completely liberated from any suspended gases in a distilling apparatus. Before the gas extracted from the discharged steam is returned to the machine it is thoroughly dehydrated.

Variations may be resorted to within the scope of the invention, and portions of the improvements may be used without others.

Having thus described my claim:-

1. A shaft stufiing box of a gas cooled electric machine having means to admit steam into said box and against said shaft at a pressure higher than that of the gas in said machine, said steam tending to escape along said shaft in one direction to the exterior atmosphere to prevent the air from entering the box and also in an opposite direction toward said gas, a condenser encircling said shaft and the exit of said box from which said steam is escaping toward said gas, and said condenser intercepting the steam escaping toward said gas.

2. A method for sealing a shaft stufiing box of a gas cooled electric machine consisting of the admission of a current of steam into said box and, against said shaft at a pressure higher than that of the gas in said machine, said steam tending to escape along said shaft in one direction to the exterior atmosphere to prevent the air from entering the box and also in an opposite direction toward said gas, intercepting the steam escaping toward said gas and liquefying it, extracting the gas from said liquefied steam, dehumidifying said extracted gas, and reconveying said dehumidified gas to said machine.

ADOLF SCHNETZLER.

invention, I 

